Make Diff.Compare able to handle a blob to blob comparison

Author: nulltoken

LibGit2Sharp.Tests/DiffBlobToBlobFixture.cs

@@ -0,0 +1,61 @@
+using System.Linq;
+using System.Text;
+using LibGit2Sharp.Tests.TestHelpers;
+using Xunit;
+
+namespace LibGit2Sharp.Tests
+{
+    public class DiffBlobToBlobFixture : BaseFixture
+    {
+        [Fact]
+        public void ComparingABlobAgainstItselfReturnsNoDifference()
+        {
+            using (var repo = new Repository(StandardTestRepoPath))
+            {
+                Blob blob = repo.Head.Tip.Tree.Blobs.First();
+
+                ContentChanges changes = repo.Diff.Compare(blob, blob);
+
+                Assert.Equal(0, changes.LinesAdded);
+                Assert.Equal(0, changes.LinesDeleted);
+                Assert.Equal(string.Empty, changes.Patch);
+            }
+        }
+
+        [Fact]
+        public void CanCompareTwoVersionsOfABlobWithADiffOfTwoHunks()
+        {
+            using (var repo = new Repository(StandardTestRepoPath))
+            {
+                var oldblob = repo.Lookup<Blob>("7909961");
+                var newblob = repo.Lookup<Blob>("4e935b7");
+
+                ContentChanges changes = repo.Diff.Compare(oldblob, newblob);
+
+                Assert.Equal(3, changes.LinesAdded);
+                Assert.Equal(1, changes.LinesDeleted);
+
+                var expected = new StringBuilder()
+                 .Append("@@ -1,4 +1,5 @@\n")
+                 .Append(" 1\n")
+                 .Append("+2\n")
+                 .Append(" 3\n")
+                 .Append(" 4\n")
+                 .Append(" 5\n")
+                 .Append("@@ -8,8 +9,9 @@\n")
+                 .Append(" 8\n")
+                 .Append(" 9\n")
+                 .Append(" 10\n")
+                 .Append("-12\n")
+                 .Append("+11\n")
+                 .Append(" 12\n")
+                 .Append(" 13\n")
+                 .Append(" 14\n")
+                 .Append(" 15\n")
+                 .Append("+16\n");
+
+                Assert.Equal(expected.ToString(), changes.Patch);
+            }
+        }
+    }
+}

LibGit2Sharp.Tests/LibGit2Sharp.Tests.csproj

@@ -45,6 +45,7 @@
   <ItemGroup>
     <Compile Include="ConfigurationFixture.cs" />
     <Compile Include="AttributesFixture.cs" />
+    <Compile Include="DiffBlobToBlobFixture.cs" />
     <Compile Include="ObjectDatabaseFixture.cs" />
     <Compile Include="DiffTreeToTreeFixture.cs" />
     <Compile Include="RepositoryOptionsFixture.cs" />

LibGit2Sharp/ContentChanges.cs

@@ -1,4 +1,6 @@
-using System.Text;
+using System;
+using System.Text;
+using LibGit2Sharp.Core;
 
 namespace LibGit2Sharp
 {
@@ -13,6 +15,59 @@ protected ContentChanges()
         {
         }
 
+        internal ContentChanges(Repository repo, Blob oldBlob, Blob newBlob, GitDiffOptions options)
+        {
+            using (var osw1 = new ObjectSafeWrapper(oldBlob.Id, repo))
+            using (var osw2 = new ObjectSafeWrapper(newBlob.Id, repo))
+            {
+                Ensure.Success(NativeMethods.git_diff_blobs(osw1.ObjectPtr, osw2.ObjectPtr, options, IntPtr.Zero, null, HunkCallback, LineCallback));
+            }
+        }
+
+        private static string NativeToString(IntPtr content, IntPtr contentlen)
+        {
+            return ((Utf8Marshaler)(Utf8Marshaler.GetInstance(string.Empty))).NativeToString(content, contentlen.ToInt32());
+        }
+
+        private int HunkCallback(IntPtr data, GitDiffDelta delta, GitDiffRange range, IntPtr header, IntPtr headerlen)
+        {
+            string decodedContent = NativeToString(header, headerlen);
+
+            PatchBuilder.AppendFormat("{0}", decodedContent);
+            return 0;
+        }
+
+        private int LineCallback(IntPtr data, GitDiffDelta delta, GitDiffRange range, GitDiffLineOrigin lineorigin, IntPtr content, IntPtr contentlen)
+        {
+            string decodedContent = NativeToString(content, contentlen);
+
+            string prefix;
+
+            switch (lineorigin)
+            {
+                case GitDiffLineOrigin.GIT_DIFF_LINE_ADDITION:
+                    LinesAdded++;
+                    prefix = Encoding.ASCII.GetString(new[] { (byte)lineorigin });
+                    break;
+
+                case GitDiffLineOrigin.GIT_DIFF_LINE_DELETION:
+                    LinesDeleted++;
+                    prefix = Encoding.ASCII.GetString(new[] { (byte)lineorigin });
+                    break;
+
+                case GitDiffLineOrigin.GIT_DIFF_LINE_CONTEXT:
+                    prefix = Encoding.ASCII.GetString(new[] { (byte)lineorigin });
+                    break;
+
+                default:
+                    prefix = string.Empty;
+                    break;
+            }
+
+            PatchBuilder.AppendFormat("{0}{1}", prefix, decodedContent);
+            return 0;
+        }
+
         /// <summary>
         ///   The number of lines added.
         /// </summary>

LibGit2Sharp/Core/NativeMethods.cs

@@ -256,7 +256,7 @@ internal delegate int git_diff_hunk_fn(
             IntPtr data,
             GitDiffDelta delta,
             GitDiffRange range,
-            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string header,
+            IntPtr header,
             IntPtr headerLen);
 
         [DllImport(libgit2)]
@@ -283,11 +283,11 @@ public static extern int git_diff_print_patch(
 
         [DllImport(libgit2)]
         public static extern int git_diff_blobs(
-            RepositorySafeHandle repository,
-            IntPtr oldBlob,
-            IntPtr newBlob,
+            GitObjectSafeHandle oldBlob,
+            GitObjectSafeHandle newBlob,
             GitDiffOptions options,
-            object data,
+            IntPtr data,
+            git_diff_file_fn fileCallback,
             git_diff_hunk_fn hunkCallback,
             git_diff_data_fn lineCallback);
 

LibGit2Sharp/Diff.cs

@@ -12,13 +12,15 @@ public class Diff
     {
         private readonly Repository repo;
 
+        internal static GitDiffOptions DefaultOptions = new GitDiffOptions { InterhunkLines = 2 };
+
         internal Diff(Repository repo)
         {
             this.repo = repo;
         }
 
         /// <summary>
-        ///   Show changes between two trees.
+        ///   Show changes between two <see cref = "Tree"/>s.
         /// </summary>
         /// <param name = "oldTree">The <see cref = "Tree"/> you want to compare from.</param>
         /// <param name = "newTree">The <see cref = "Tree"/> you want to compare to.</param>
@@ -37,16 +39,22 @@ private DiffListSafeHandle BuildDiffListFromTrees(ObjectId oldTree, ObjectId new
             using (var osw2 = new ObjectSafeWrapper(newTree, repo))
             {
                 DiffListSafeHandle diff;
-                GitDiffOptions options = BuildDefaultOptions();
+                GitDiffOptions options = DefaultOptions;
                 Ensure.Success(NativeMethods.git_diff_tree_to_tree(repo.Handle, options, osw1.ObjectPtr, osw2.ObjectPtr, out diff));
 
                 return diff;
             }
         }
 
-        private GitDiffOptions BuildDefaultOptions()
+        /// <summary>
+        ///   Show changes between two <see cref = "Blob"/>s.
+        /// </summary>
+        /// <param name = "oldBlob">The <see cref = "Blob"/> you want to compare from.</param>
+        /// <param name = "newBlob">The <see cref = "Blob"/> you want to compare to.</param>
+        /// <returns>A <see cref = "ContentChanges"/> containing the changes between the <paramref name = "oldBlob"/> and the <paramref name = "newBlob"/>.</returns>
+        public ContentChanges Compare(Blob oldBlob, Blob newBlob)
         {
-            return new GitDiffOptions { InterhunkLines = 2 };
+            return new ContentChanges(repo, oldBlob, newBlob, DefaultOptions);
         }
     }
 }